The present invention regards a device for cutting of fish heads. In particular, it regards a device for selective cutting of fish heads, particularly salmon or trout from fish farms In the fish processing industry, there are various types of fish processing machines that have several functions, including cutting of heads. These machines are generally fed fish of a uniform size and type, and the head cutting is then part of a process that often produces ready skinned fillets.

Today, there are a few major foreign operators in the market when it comes to producing fish processing machines.

For, the slaughtering of salmon, use is made of head cutting machines and gutting apparatuses, and these represent the. main contribution when it comes to automating the fines.

The present device for selective cutting of fish heads will ensure an increase in the degree of automation, which in turn will make for a greater earning potential.

Within the salmon industry, there is a desire to be as flexible as possible in terms of which fish which is to have their heads cut off and be frozen, the alternative being not cutting the head off and packing it in polystyrene boxes as fresh fish. The division of the day's production between"fresh"and"frozen"can vary from day to day. It ranges from 0 to 100% head cutting, depending on the product to be produced. The latter production (100% head cutting) applies in particular to the production of trout. There is a great potential for automating the cutting of heads from salmon and trout, particularly as new gutting apparatuses are on the market, which may be connected directly with the head cutting.

It is for this production that the device for selective cutting of fish heads according to the invention is intended. The head cutting device will allow a reduction in manpower, give greater flexibility and simplify the production line, thereby giving considerable cost savings in the production.

There are several types of head cutting devices in use in the salmon industry, however the one feature they all have in common is that they must be fed manually, by one or possibly two operators, The speed ranges from 15 to 60 fish per minute. In plants that produce a lot of trout, the decision is often made to cut the heads off all the fish before gutting.

If, on the other hand, the. primary emphasis is on salmon, the choice is to gut, clean and cool the fish, in order then to grade it on the basis of its size. Thereafter, the heads are cut off those fish that are of the size designated to be frozen.

The cutting of fish heads at an early stage of the production (before gutting) works well in trout production, where up to 100% of the fish is frozen after having the head cut off.

If, however, only a portion of the products is to have the head cut off, this operation should be performed on the basis of quality and/or weight grading. If several sizes of fish are to have their heads cut off, the decision is often to use several head cutting devices in order to avoid having to again grade the fish according to size after the head cutting.

The drawback of this way of handling the head cutting is the fact that the fish is brought out into the packing area, which violates the zoning of the production plant, as both packing and processing of the fish is being performed in one and the same zone. In addition, it is a costly production method with respect to manpower. A production plant for butchering and processing of fish is generally partitioned into three zones in order to ensure good quality and prevent contamination of the fish. In the first zone, the live fish comes in to cut the throat. In the second zone, the fish is gutted, cleaned, cooled and, if necessary, has its head cut off. In me third zone, the cleaned and clean fish is packed, i. e. the fish is ready processed when it enters this zone.

The actual cutting of the fish heads is performed either by using rotating knives or according to the guillotine principle. The execution of the head cutting is important, and must be carried out in a particular manner. The cut must have two different angles; one from the underside of the curve of the gills until the cut intersects the cut from the neck at a different angle. The cut as described is used on fish that is to be frozen whole; in this case the eagle bone ("rnebein") remains on the fish. If, on the other hand, the fish is to be processed into fillets, the cut from the abdominal side is altered so as also to cut away the area in which the eagle bone is located- The head cutting devices that are presently on the market exhibit great variations both in terms of design, capacity and price. The prices vary from several hundred thousand Norwegian kroner for a machine with rotating knives and down to less than one hundred thousand for simple models based on the guillotine principle.

The invention is thus aimed at a device for selective cutting of fish heads, preferably salmon or trout, which device is associated with a gutting apparatus and then a packing device, characterised in that the device for selective cutting of heads consists of a V- shaped area between an upper conveyor belt and a lower belt for supplementary cleaning, in which area the fish is arranged with the abdominal side up, a stop tool for fixing the fish by the gills, a lower knife and at least one overhead knife, in addition to a control unit that compares preset values with the weight of the fish at hand, automatically selecting whether or not to cut the fish head.

The weight of the fish can be determined by various methods such as weighing, measuring of the length, width or circumference, or by means of photography or light sensor measurements.

The novel device for selective cutting of fish heads according to the invention is such that it may in principle be combined with any gutting apparatus for salmon or trout that is already on the market. The invention aims at providing a head cutting device that may be connected up to any known gutting apparatus, and the principle will also be interesting in other types of fish production.

The head cutter must have the simplest possible construction, prioritising operational stability as well as the requirement for little maintenance. At the same time it must be automatic and not require an operator.

The device for selective cutting of fish heads according to the invention will be favourably priced, and it is expected that the investment will give a pay back within a relatively short time.

The head cut must be in accordance with today's requirements, and the possibilities of adjusting the cut angle of the knife will also satisfy the requirement for flexibility. The cut will be performed by use of rotating knives driven by electric motors.

The head cutting device will automatically select the fish which is to be fed to the head cutting device, based on the weight of the fish. The weight of the fish is based either on the measurements of the fish (length and width) made by the gutting apparatus, in combination with statistics that in tum give the estimated weight of the fish, or alternatively the feed belt of the device for selective head cutting may be supported on weight cells that indicate the weight of the fish. The net weight of the feed belt is tared, so as to leave only the weight of the fish, which is then evaluated by the system before the fish passes down the production line or continues to the head cutting device. It is further possible to determine the weight of the fish by optical measurements. The measured values are compared with the preset values, and the machine then decides whether the fish is to have its head cut off or not The invention will now be explained in greater detail by means of drawings, in which : Figure 1 shows the principle of a known gutting apparatus ; Figures 2A, B, C show the device for selective cutting of fish heads according to the invention; and Figure 3 shows the principle of selecting fish for head cutting.

Figure 1 shows a known gutting apparatus 10. In the machine, the fish 11 is pulled through the gutting process by it being held in the spur 12 by a spur lock 13. The fish is positioned with the abdominal side and rests against side membersl4, 15 on the conveyor belt 16. The fish is gutted automatically, and the guts are removed for instance by suction, using a vacuum pump. When the fish 11 has been gutted, the spur lock 13 is released, and the fish is forced out of the rest position by the ejector 18. The fish then falls into a new, lower V-shaped conveyor belt (not shown), still with the abdominal side up, in order to be transported to an operator (not shown) who handles the manual control and supplementary cleaning.

The present invention involves increasing the length between the upper conveyor belt 16 and the lower supplementary cleaning belt 17 as indicated in Figures 2A, 2B and 2C, all of which are shown in the direction of transport. The device 20 for selective cutting of fish heads is arranged between. these belts, at a suitable. distance. As both upper conveyor belt 16 and lower cleaning belt 17 are free-standing components, this is done simply by fitting leg extensions to the gutting apparatus. When the fish is forced out by the ejector 18, it ends up between two angled conveyor belts 22,23, the latter of which is rotatably attached to a hinge point 24. These conveyor belts 22,23 between them form an angle of approximately 45 degrees, and one of the belts 23 is mounted in a manner that allows rotation by means of a cylinder By rotating one belt, the distance between the belts 22, 23 increases, so that any fish 11 that are not to have their heads cut off can fall down onto the cleaning belt 17. Here, the fish goes through manual supplementary cleaning and is visually checked by an operator before passing further along the production line.

Figure 3 is a side view of the device 20 for selective cutting of fish heads. Fish that is to undergo head cutting is carried by the same angled belts 22, 23 into the end section of the belts which constitutes the device 20 for selective head cutting. In this section, the fish is held by a stop tool 19. This is effected by the stop tool 19 holding back the fish by its gills, which in turn provides the rotating knives 25,26 with a point of reference to ensure that the cut is made correctly. The device for selective cutting of fish heads is equipped with two overhead knives 25, 26, with knife 25 making a diagonal cut that entails the eagle bone of the fish remaining on the body of the fish. The rotating knife 26 makes a straight cut that removes the eagle bone from the body-These rotating knives 25,26 work independently of each other, depending on the desired cut and whether the eagle bone is to be removed or not. The lower knife 27 makes a vertical cut from the back, and is used regardless of which cut has been chosen from the abdominal side. The cuts from all of these knifes 25, 26,27 are made far enough into the body so as to make them intersect the opposite cut. In an alternative embodiment, the two overhead rotating knives 25 and 26 can be replace by one knife for which the cut angle may be adjusted automatically.

A further alternative to using rotating knives that cut the fish from two sides is to use a head cutter that works according to the guillotine principle, i. e. one knife that cuts the entire head off with one cut.

The device 20 for selective cutting of fish heads will itself decide which fish are to have their heads cut off, and which type of cut will be used, all depending on preset parameters. This is preferably done on the basis of weight, but the quality of a sort grade (skin colour) can also give the head cutter 20 a signal to perform the head cutting.

The condition of this is that the quality graduation, e. g. the colour reading, is input into the programmable logic controller 31 (plc) that controls the entire system. The grading of the fish is further carried out in such a manner that there is always a check on the fish going through the gutting apparatus.

The weight of the fish may be determined in several ways. The most obvious solution is to make use of those measurements that may already have been made by the gutting apparatus, in order then to combine this data with statistics. This will give a good indication of weight, which may be used for selecting the fish that is to go to head cutting. An alternative to this method is to extend, as well as split the angle between the belts 22, 23 of the device for selective head cutting, and then to suspend the first part of the angle belts from weighing modules that weigh the fish when it is on its way into the device 20 for selective head cutting. Furthermore, the weight may be determined indirectly, by measuring the length, width or circumference of the fish ; based on which parameters the weight of the fish may be determined with a sufficient degree of accuracy. It is also possible to find the weight optically, by for instance photographing the fish or if possible letting it pass by photoelectric cells that determine the weight of the fish by means of light signals.

The fish 11 can as mentioned earlier be dropped down onto the lower cleaning belt 17 by the hinged belt 22,23 in those cases where the fish is not to have its head cut. If the fish has its head cut off, it also will be dropped down onto the lower cleaning belt 17 in the same way. Due to the various drop zones, the cleaning belt 17 extends underneath the entire length of the head cutter 20. The cleaning belt 17 transports the fish further on to the operators that perform the supplementary cleaning if required. The cleaners will then be able to both clean the fish manually and perform a visual quality control of both the abdominal cut and the head cut in one and the same operation. Then the fish is carried further along the production lines.

The essential point of the present invention is the selectivity. of the head cutting. This is achieved by using weight measurements from the gutting apparatus or possibly weighing or optical measurements for weight determination, to decide whether to send the fish to head cutting or leave it with the head on, depending on the wishes defined by the operator through the control programme.